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<head><meta charset="utf-8"><title>Region inference · t-compiler/wg-nll · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/index.html">t-compiler/wg-nll</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html">Region inference</a></h3>

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<a name="136086745"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136086745" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136086745">(Oct 19 2018 at 03:22)</a>:</h4>
<p>From the <a href="https://rust-lang-nursery.github.io/rustc-guide/borrow_check/region_inference.html#final-example" target="_blank" title="https://rust-lang-nursery.github.io/rustc-guide/borrow_check/region_inference.html#final-example">rustc-guide</a>, can someone explain to me in this example:<br>
<code>for&lt;'a&gt; fn(&amp;'a u32, &amp;'a u32) -&gt; &amp;'a u32
    &lt;:
fn(&amp;'!1 u32, &amp;'!2 u32) -&gt; &amp;'!1 u32</code></p>
<p>How this happens, <br>
<code>&amp;'!1 u32 &lt;: &amp;'?3 u32 // arg 1 (makes sense)
&amp;'!2 u32 &lt;: &amp;'?3 u32 // arg 2 (makes sense)
&amp;'?3 u32 &lt;: &amp;'!1 u32 // return type (doesn't make sense, unless we say they are subtypes)</code></p>
<p>The last line that is for the return type, is <br>
<code>&amp;'?3 u32 &lt;: &amp;'!1 u32 // return type</code><br>
and NOT<br>
<code>&amp;'!1 u32 &lt;: &amp;'?3 u32  // return type</code></p>



<a name="136086804"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136086804" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136086804">(Oct 19 2018 at 03:24)</a>:</h4>
<p>And this one<br>
<code>V1 in U1 = {skol(1)}
V2 in U2 = {skol(2)}
V3 in U2 = {}</code></p>
<p>Why is V3 in <strong>U2</strong> and not in <strong>U1</strong> ?</p>



<a name="136104964"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136104964" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> csmoe <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136104964">(Oct 19 2018 at 11:25)</a>:</h4>
<p>this difference between <code>arg1/2</code> and <code>return type</code> caused by <code> fn(T) -&gt; U is contravariant over T, but covariant over U</code></p>



<a name="136104981"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136104981" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> csmoe <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136104981">(Oct 19 2018 at 11:25)</a>:</h4>
<p><span class="user-mention" data-user-id="128294">@blitzerr</span> cc <a href="https://doc.rust-lang.org/nomicon/subtyping.html#variance" target="_blank" title="https://doc.rust-lang.org/nomicon/subtyping.html#variance">https://doc.rust-lang.org/nomicon/subtyping.html#variance</a></p>



<a name="136105693"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136105693" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> csmoe <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136105693">(Oct 19 2018 at 11:40)</a>:</h4>
<p>btw, <span class="user-mention" data-user-id="116009">@nikomatsakis</span>  it seems you had cleared <code>skolemize</code> with <code>placeholder</code> in rustc, should that be apply to rustc-guide?<br>
and function is covariant over its return type should be mentioned in this example as arguments.</p>



<a name="136105720"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136105720" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136105720">(Oct 19 2018 at 11:40)</a>:</h4>
<p><span class="user-mention" data-user-id="116773">@csmoe</span> yep that should be applied to rustc-guide</p>



<a name="136107099"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136107099" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136107099">(Oct 19 2018 at 12:12)</a>:</h4>
<p>Thanks <span class="user-mention" data-user-id="116773">@csmoe</span> that doc does explain the first part. But I still don't get this one. Why is V3 working with U2 and not U1 ?</p>
<p><code>V1 in U1 = {skol(1)}
V2 in U2 = {skol(2)}
V3 in U2 = {}</code></p>
<p>Why is V3 in <strong>U2</strong> and not in <strong>U1</strong> ?</p>



<a name="136109540"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136109540" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> csmoe <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136109540">(Oct 19 2018 at 13:03)</a>:</h4>
<p><span class="user-mention" data-user-id="128294">@blitzerr</span> sorry, this ques'n is beyond my knowledge, maybe you can refer to <span class="user-mention" data-user-id="116009">@nikomatsakis</span></p>



<a name="136111032"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111032" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111032">(Oct 19 2018 at 13:28)</a>:</h4>
<p><span class="user-mention" data-user-id="128294">@blitzerr</span> the subtyping algorithm instantiates the binders in the <strong>subtype</strong> as <strong>existentials</strong> in some universe that can name all the things in the super type</p>



<a name="136111039"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111039" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111039">(Oct 19 2018 at 13:28)</a>:</h4>
<p>one way to think about it is this:</p>



<a name="136111043"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111043" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111043">(Oct 19 2018 at 13:28)</a>:</h4>
<p>if you have <code>for&lt;A&gt; T &lt;: for&lt;B&gt; U</code> (in general...)</p>



<a name="136111065"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111065" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111065">(Oct 19 2018 at 13:29)</a>:</h4>
<p>that is true if <code>forall&lt;B&gt; { exists&lt;A&gt; { T &lt;: U } }</code></p>



<a name="136111088"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111088" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111088">(Oct 19 2018 at 13:29)</a>:</h4>
<p>that is, if "for all lifetimes B", whatever they are, there exists <em>some</em> lifetimes A, such that <code>T &lt;: U</code></p>



<a name="136111094"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111094" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111094">(Oct 19 2018 at 13:29)</a>:</h4>
<p>the reason for this is: we have a value of the <strong>subtype</strong> (<code>T</code>)</p>



<a name="136111105"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111105" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111105">(Oct 19 2018 at 13:29)</a>:</h4>
<p>we are storing it into a slot that is typed with the <strong>supertype</strong> (<code>U</code>)</p>



<a name="136111181"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111181" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111181">(Oct 19 2018 at 13:30)</a>:</h4>
<p>so we have to be sure that the subtype is an instance of the supertype</p>



<a name="136111205"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111205" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111205">(Oct 19 2018 at 13:30)</a>:</h4>
<p>to use a concrete example, if you had</p>



<a name="136111212"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111212" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111212">(Oct 19 2018 at 13:30)</a>:</h4>
<p>for&lt;'a&gt; fn(&amp;'a u32) &lt;: fn(&amp;'static u32)</p>



<a name="136111225"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111225" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111225">(Oct 19 2018 at 13:30)</a>:</h4>
<p>that should be true, because on the one hand we have a fn that accepts <strong>any</strong> region</p>



<a name="136111241"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111241" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111241">(Oct 19 2018 at 13:31)</a>:</h4>
<p>and we are using it in a spot where it will only have to accept the <strong>static region</strong></p>



<a name="136111246"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111246" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111246">(Oct 19 2018 at 13:31)</a>:</h4>
<p>since the static region is a region, that should be fine</p>



<a name="136111251"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111251" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111251">(Oct 19 2018 at 13:31)</a>:</h4>
<p>(but the reverse is not true -- if the fn only accepts <code>'static</code>, it cannot be used in a spot where it maybe given anything)</p>



<a name="136111316"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111316" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111316">(Oct 19 2018 at 13:32)</a>:</h4>
<blockquote>
<p>since the static region is a region, that should be fine</p>
</blockquote>
<p>expressed the way I put it before:</p>
<p><code>forall&lt;&gt; { exists&lt;'a&gt; { fn(&amp;'a u32) &lt;: fn(&amp;'static u32) } }</code></p>



<a name="136111324"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136111324" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136111324">(Oct 19 2018 at 13:32)</a>:</h4>
<p>the outer <code>forall</code> is empty because the supertype here doesn't have any bound regions</p>



<a name="136113068"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113068" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113068">(Oct 19 2018 at 13:59)</a>:</h4>
<p>Thanks <span class="user-mention" data-user-id="116009">@nikomatsakis</span>  that makes sense. How do we read “&lt;:” ?</p>



<a name="136113519"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113519" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113519">(Oct 19 2018 at 14:05)</a>:</h4>
<p>you mean how is <code>&lt;:</code> pronounced?</p>



<a name="136113604"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113604" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113604">(Oct 19 2018 at 14:06)</a>:</h4>
<p><code>S &lt;: T</code>, for types <code>S</code> and <code>T</code>, is usually pronounced "S is a subtype of T"</p>



<a name="136113608"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113608" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113608">(Oct 19 2018 at 14:06)</a>:</h4>
<p>Right</p>



<a name="136113648"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113648" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113648">(Oct 19 2018 at 14:07)</a>:</h4>
<p>e.g. <a href="https://en.wikipedia.org/wiki/Subtyping" target="_blank" title="https://en.wikipedia.org/wiki/Subtyping">https://en.wikipedia.org/wiki/Subtyping</a></p>



<a name="136113654"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113654" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113654">(Oct 19 2018 at 14:07)</a>:</h4>
<p>Ahh Subtype, I was thinking sunset.</p>



<a name="136113664"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113664" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113664">(Oct 19 2018 at 14:07)</a>:</h4>
<p>there's a relationship :)</p>



<a name="136113668"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113668" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113668">(Oct 19 2018 at 14:07)</a>:</h4>
<p>Thanks <span class="user-mention" data-user-id="116083">@pnkfelix</span></p>



<a name="136113672"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113672" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113672">(Oct 19 2018 at 14:07)</a>:</h4>
<p>i.e., the set of values with type T is a subset of those with type U, if T &lt;: U</p>



<a name="136113719"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113719" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113719">(Oct 19 2018 at 14:08)</a>:</h4>
<p>oh oh, <em>sub</em>set</p>



<a name="136113727"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113727" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113727">(Oct 19 2018 at 14:08)</a>:</h4>
<p>/me was super confused</p>



<a name="136113746"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113746" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113746">(Oct 19 2018 at 14:08)</a>:</h4>
<p>to the tune of "sunrise, subset"... "super-subset"</p>



<a name="136113770"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136113770" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136113770">(Oct 19 2018 at 14:09)</a>:</h4>
<p>Subtype*.  This autocorrect <span class="emoji emoji-1f600" title="grinning">:grinning:</span></p>



<a name="136115391"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136115391" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136115391">(Oct 19 2018 at 14:37)</a>:</h4>
<p>Thanks a lot <span class="user-mention" data-user-id="116009">@nikomatsakis</span>  and <span class="user-mention" data-user-id="116083">@pnkfelix</span></p>



<a name="136117860"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136117860" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136117860">(Oct 19 2018 at 15:15)</a>:</h4>
<p>I am traveling and on way to somewhere but after I read up on all this, will post further questions if I had any. Thanks <span class="user-mention" data-user-id="116773">@csmoe</span> <span class="user-mention" data-user-id="116009">@nikomatsakis</span>  and <span class="user-mention" data-user-id="116083">@pnkfelix</span>  for clarifications.</p>



<a name="136117929"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136117929" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136117929">(Oct 19 2018 at 15:16)</a>:</h4>
<p>And sorry for the /subset/sunset/ confusion. <span class="emoji emoji-1f602" title="joy">:joy:</span></p>



<a name="136118037"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136118037" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> pnkfelix <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136118037">(Oct 19 2018 at 15:18)</a>:</h4>
<p>i love staring for hours at a good subset</p>



<a name="136119096"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136119096" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136119096">(Oct 19 2018 at 15:34)</a>:</h4>
<p>Usually with some wine <span class="emoji emoji-1f44c" title="ok">:ok:</span></p>



<a name="136119098"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/122657-t-compiler/wg-nll/topic/Region%20inference/near/136119098" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> blitzerr <a href="https://rust-lang.github.io/zulip_archive/stream/122657-t-compiler/wg-nll/topic/Region.20inference.html#136119098">(Oct 19 2018 at 15:34)</a>:</h4>
<p>I have always liked every subset I have met <span class="emoji emoji-1f609" title="wink">:wink:</span></p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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